全文获取类型
收费全文 | 855篇 |
免费 | 87篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 10篇 |
化学工业 | 172篇 |
金属工艺 | 45篇 |
机械仪表 | 72篇 |
建筑科学 | 12篇 |
能源动力 | 35篇 |
轻工业 | 109篇 |
水利工程 | 7篇 |
石油天然气 | 1篇 |
无线电 | 129篇 |
一般工业技术 | 221篇 |
冶金工业 | 54篇 |
原子能技术 | 12篇 |
自动化技术 | 64篇 |
出版年
2024年 | 3篇 |
2023年 | 22篇 |
2022年 | 23篇 |
2021年 | 32篇 |
2020年 | 18篇 |
2019年 | 33篇 |
2018年 | 43篇 |
2017年 | 33篇 |
2016年 | 41篇 |
2015年 | 43篇 |
2014年 | 58篇 |
2013年 | 64篇 |
2012年 | 86篇 |
2011年 | 84篇 |
2010年 | 54篇 |
2009年 | 50篇 |
2008年 | 40篇 |
2007年 | 40篇 |
2006年 | 24篇 |
2005年 | 32篇 |
2004年 | 16篇 |
2003年 | 24篇 |
2002年 | 11篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 13篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1990年 | 2篇 |
1987年 | 3篇 |
排序方式: 共有943条查询结果,搜索用时 15 毫秒
91.
92.
Duchang Heo Il Ki Han Jung Il Lee Jichai Jeong 《Photonics Technology Letters, IEEE》2004,16(8):1801-1803
We studied symmetric and asymmetric InGaAsP-InGaAs 1.55-/spl mu/m multiquantum-well (MQW) laser diodes (LDs) with highly p-doped layers in the two-step separate confinement heterostructure (SCH). The p-doping in p-SCH suppresses the electron overflow from the MQWs to p-SCH, but it is an origin of free carrier absorption loss. An additional InGaAsP layer inserted inside n-SCH makes asymmetric field distribution and, therefore, reduces the portion of optical field distribution in highly p-doped regions with high optical loss. Compared with symmetric structure, asymmetric SCH LD has low threshold current density, low internal loss, and high and flat slope efficiency with respect to temperature. 相似文献
93.
Keun Byoung Yoon In-Kui Cho Seung Ho Ahn Myung Yong Jeong Deug Ju Lee Young Un Heo Byung Sup Rho Hyo-Hoon Park Byoung-Ho Rhee 《Lightwave Technology, Journal of》2004,22(9):2119-2127
As discussed in this paper, a practical optical backplane system was demonstrated, using a waveguide-embedded optical backplane board, processing boards, and optical slots for board-to-board interconnection. A metal optical bench was used as a packaging die for the optical devices and the integrated circuit chips in both the transmitter and the receiver processing boards. The polymer waveguide was produced by means of a hot-embossing technique and was then embedded following a conventional lamination processes. The average propagation loss of these waveguides was approximately 0.1 dB/cm at 850 nm. The dimension and optical properties of the waveguide in an optical backplane board were unchanged after lamination. As connection components between transmitter/receiver processing boards and an optical backplane board, optical slots were used for easy and repeatable insertion and extraction of the boards with a micrometer-scale precision. A 1/spl times/4 850-nm vertical-cavity surface-emitting laser array was used with 2 dBm of output power for the transmitter and a p-i-n photodiode array for the receiver. This paper successfully demonstrates 8 Gb/s of data transmission between the transmitter processing board and the optical backplane board. 相似文献
94.
Efficient design of device-to-device (D2D) communication calls for D2D users to propose adaptive power allocation strategy and to establish reliable communication links while protecting the QoS of cellular communications. In this paper, we consider the D2D communication as an underlay to relay-assisted cellular networks. To maximize the ergodic capacity, we derive an optimal transmission power under an average power constraint. With the derived optimal transmission power, a transmission period selection strategy for D2D communication is firstly introduced to improve reliability. We derive the outage probability in closed forms and evaluate the ergodic capacity to show performances of the proposed system. Numerical results show that the D2D system can achieve high capacity gains by flexibly allocating transmission power based on channel state information and significantly enhance reliability by selecting a transmission period, while satisfying various QoS conditions for cellular communication. 相似文献
95.
This paper presents a Rate-Compatible Block Turbo Code (RC-BTC) with increased transmission capacity. The proposed RC-BTC uses a new algorithm called information augmenting scheme, and can achieve a higher code rate than conventional one. A new Error Location Finding (ELF) Decoding Algorithm is introduced to solve the decoding problem of the information augmenting scheme. As a result, a novel error-correcting capability of the BTC-applied Chase-ELF Hybrid Decoder, combining the previous Chase–Pyndiah algorithm and the proposed ELF algorithm, is demonstrated via Monte-Carlo simulation. In addition, the proposed code maximally increases the transmission capacity with the Chase-ELF Hybrid decoder using an information augmenting scheme. 相似文献
96.
Nanoparticles of Conjugated Polymers Prepared from Phase‐Separated Films of Phospholipids and Polymers for Biomedical Applications
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
97.
K. V. Khot S. S. Mali N. B. Pawar R. M. Mane V. V. Kondalkar V. B. Ghanwat P. S. Patil Chang Kook Hong Jin Hyeok Kim Jaeyeong Heo P. N. Bhosale 《Journal of Materials Science: Materials in Electronics》2014,25(9):3762-3770
In the present investigation, we have successfully synthesized lead sulfide (PbS) thin films by using simple, cost effective and facile aqueous chemical route. The effect of deposition time on optical, structural and morphological properties of PbS thin films were investigated by using UV–Vis–NIR absorption spectroscopy, X-ray diffraction (XRD), photoluminescence, field emission scanning electron microscopy (FESEM), high-resolution-transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The optical band gap energy was varied in the range of 0.96–1.56 eV. The XRD patterns revealed the formation of pure cubic crystal structure. FESEM micrographs demonstrated the conversion of morphology from pyramidal to interconnected nanocubic. HRTEM and selected area electron diffraction (SAED) pattern illustrated that nanoparticles are compact, well interconnected and single crystalline in nature. EDS spectrum confirms that deposited PbS thin films are in good stoichiometry. 相似文献
98.
I. O. Parm K. Kim D. G. Lim J. H. Lee J. H. Heo J. Kim D. S. Kim S. H. Lee J. Yi 《Solar Energy Materials & Solar Cells》2002,74(1-4)
The silicon nitride films were deposited by means of high-density inductively coupled plasma chemical vapor deposition in a planar coil reactor. The process gases used were pure nitrogen and a mixture of silane and helium. Passivated by silicon nitride, solar cells show efficiency above 13%. Strong H-atom release from the growing SiN film and Si–N bond healing are responsible for the improved electrical and passivation properties of SiN film. This paper presents the optimal refractive index of SiN for single layer antireflection coating as well as double layer antireflection coating in solar cell applications. 相似文献
99.
100.
We report a simple but efficient method to prepare metallic nanowire-graphene (MN-G) hybrid nanostructures at a low temperature and show its application to the fabrication of flexible field emission devices. In this method, a graphene layer was transferred onto an anodic alumina oxide template, and vertically aligned Au nanowires were grown on the graphene surface via electrodeposition method. As a proof of concept, we demonstrated the fabrication of flexible field emission devices, where the MN-G hybrid nanostructures and another graphene layer on PDMS substrates were utilized as a cathode and an anode for highly flexible devices, respectively. Our field emission device exhibited stable and high field emission currents even when bent down to the radius of curvature of 25 mm. This MN-G hybrid nanostructure should prove tremendous flexibility for various applications such as bio-chemical sensors, field emission devices, pressure sensors and battery electrodes. 相似文献